I. Field of the Invention
The present invention relates to a housing for an electronic circuit.
II. Description of Related Subject Matter
There are many applications in the automotive industry and elsewhere where it is necessary to encapsulate electronic circuits within metal housings to protect the electronic circuits not only from mechanical impact and debris, but also from electromagnetic interference (EMI). One such exemplary electronic circuit contained within a metal housing is illustrated in FIG. 1.
With reference then to FIG. 1, these previously known housings for electrical components typically comprise a metal base 20 having an open top 22. A metal lid 24 is then positioned over the base 20 to form an interior chamber 26 dimensioned to contain one or more electronic circuits 28.
In order to protect the electronic circuits from debris, moisture and the like, a resilient seal 30 is disposed between the base 20 and lid 24. The base 20 and lid 24 are then secured together by a plurality of fasteners 32, typically bolts, which ideally compress the seal 30 and prevent debris and moisture from entering into the chamber 26. After sealing the base 20 and lid 24 together, the electronic circuits 28 are electrically accessible through an electrical port 34 attached to the housing.
In practice, however, these previously known housings for electronic circuits have not proven wholly satisfactory in use. One disadvantage of these previously known housings is that the lid 24 and/or base 20 may deform slightly when the fasteners 32 are tightened. When this occurs, a gap may form between the seal 30 and either the base 20 or lid 24. Such a gap disadvantageously allows debris, moisture and the like to enter into the chamber 26 and damage the circuits 28.
A still further disadvantage of these previously known housings for electronic circuits is that foreign particles may accumulate in the area 36 adjacent the outer periphery of the seal 30. Such particles can, over time, corrode the base 20 and/or lid 24 and permit entry of debris, moisture and the like into the chamber 26. Furthermore, in automotive applications, road salt and water can accelerate such corrosion.
A still further disadvantage of these previously known housings is that a physical gap exists between the base 20 and lid 24 following assembly. This physical gap enables EMI to enter into the circuit chamber 26 and cause malfunction of certain circuits 28.
A still further disadvantage of these previously known housings for electronic circuits is that the fasteners 32, as well as the cost of assembling with the fasteners, appreciably increases both the overall cost and weight of the housing. Additionally, even when the fasteners 32 are properly tightened, some movement may still occur between the base 20 and lid 24. This movement can result in vibration between the base 20 and lid 24 and potential damage to the electronic circuits 28, particularly when the housing is subjected to harsh operating environments, such as the engine compartment of an automotive vehicle.
A still further disadvantage of these previously known housings for electronic circuits is that the lid 24 is separable from the base 20 by simply loosening the fasteners 32. This, in turn, allows tampering of the electronic circuits 28. Such tampering is highly undesirable in many situations, for example where the electronic circuit 28 contains odometer information stored in nonvolatile memory. Tampering of the circuits 28 would thus enable the memory to be altered to reflect a lower distance traveled by the vehicle.